Understanding Nutritional Requirements of Spiny Lobster Larvae

Abstract

Recently the world’s three largest spiny lobster fisheries, including the western Australian spiny lobster, Panulirus cygnus, and the southern Australasian spiny lobster, Jasus edwardsii, have gone into marked decline which appears to have been driven by a dramatic decrease in recruitment. Nutrient deficiency of spiny lobster larvae has been blamed both for the consistent occurrence of high mortalities in larval culture and for the inadequate accumulation of lipid energy reserves in spiny lobster pueruli leading to the decline of spiny lobster recruitment. Therefore, to help understand the nutrient requirements of spiny lobster phyllosomas, the current research identified the nutritional composition of potential zooplankton prey of phyllosomas of spiny lobster J. edwardsii from New Zealand waters, and the nutritional condition of spiny lobster P. cygnus from three mid- to late- stages of larval development (stages VI, VII, VIII) sampled from two cold core cyclonic eddies and two warm core anticyclonic eddies of the Leeuwin Current off the Western Australian coast. Key findings of this research were:  Potential zooplankton prey of phyllosomas of J. edwardsii in the most part provides a reliable source of protein. However, only a small range of zooplankton taxa had a high lipid yield, suggesting that this narrow range of zooplankton are likely to be targeted by phyllosomas, especially during the late-stages of development when accumulation of lipid is crucial for adequately resourcing the subsequent puerulus.  Most potential zooplankton prey of phyllosomas of J. edwardsii had a high content of phospholipid (ranging from 28.0 % to 94.8 %). Phyllosomas require a diet rich in lipid (probably >10 %) preferably as PL and high in DHA, EPA, as well as a small group of fatty acids associated with energy storage in the puerulus of J. edwardsii. It is speculated that the reduced phosphorous availability in the epipelagic ocean, associated with global ocean warming, could limit PL formation and could ultimately be a factor in the decline of spiny lobster recruitment. Analyses of phyllosomas of the spiny lobster P. cygnus from Western Australia revealed significant accumulation of lipid, and especially a small group of fatty acids associated with energy storage in the subsequent puerulus stage, occuring from larval stages VI to VIII.  Panulirus cygnus phyllosomas sampled from cyclonic eddies of the Leeuwin Current off Western Australia were found to have larger body mass, higher protein, and higher lipid content compared with phyllosomas from adjacent anticyclonic eddies. Examination of fatty acid food chain markers from lipid taken from phyllosomas showed a higher level of flagellate markers and a lower level of copepod-based food chain markers from cyclonic eddies versus anticyclonic eddies. The results indicate that the microbial food web in cyclonic eddies could lead to better feeding conditions for phyllosomas, which may lead to phyllosomas in better nutritional condition, and may ultimately improve their chances of recruitment into the coastal environment.  Overall, the results of this study provide information on the nutrient requirements of phyllosomas with the potential to assist in the formulation of artificial feed for the larviculture of spiny lobsters. It is also suggested from the results of the research that the larval feeding environment is very important for phyllosoma nutritional condition and the changing global environment could be one of the reasons for the decline of recruitment to spiny lobster populations.